Fixes broken skip link to content

[Isabella-Mitchell]

Resolves JIRA N/A

Noticed when using WAVE tool i.e. https://wave.webaim.org/report#/https://www.bbc.com/ws/languages

Overall changes

Fixes broken 'skip to content' link on this page https://www.bbc.com/ws/languages

Code changes

• Adds id of 'content' to heading

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